Computational Theory Research Articles

Nanofibrous Covalent Organic Frameworks Based Hierarchical Porous Separators for Fast‐Charging and Thermally Stable Lithium Metal Batteries

AbstractEngineering multifunctional smart separators are important for the ongoing pursuit of fast‐charging and safe batteries. Herein, a novel nanofibrous covalent organic framework (COF) based separator with well‐designed hierarchical porous channels is fabricated to effectively regulate mass transport for fast‐charging and thermally stable lithium metal batteries (LMBs). Such a hierarchical porous separator consists of electrospun polyacrylonitrile nanofibers with macroporous channels (average diameter of 323 nm) and mesoporous channels (≈7 nm) created between amide‐group‐bonded COF nanoparticles with intrinsic 1.6 nm lithiophilic microporous channels (PAN/AM‐COF). Computational fluid dynamics and density functional theory calculations demonstrate that PAN/AM‐COF can simultaneously facilitate high‐speed and selective transport of Li+, as well as homogeneous deposition of Li, achieving high conductivity (3.33 mS cm−1) and high Li+ transference number (0.79). As a result, Li || LFP full cell with PAN/AM‐COF displays superior cycling stability at 10 C with an acceptable capacity attenuation (0.037% per cycle) over 1000 cycles. Moreover, when operating under an extreme temperature of 100 °C, the Li || LFP full cell with PAN/AM‐COF can still operate stably for 300 cycles at 30 C, highlighting its potential processing scalability for ultrafast‐charging energy storage systems. This study gives insights into designing functional separators for fast‐charging LMBs.

Analysis of the structural reliability of communication networks supporting protective switching mechanisms for one protected section and one backup section

Objectives. The service level agreement is an important tool used in building reasonable relations between subscribers and operators of telecommunication networks. This includes the quality of services provided. One key component is reliability as assessed by the availability factor. The most suitable model for assessing the reliability of the service provided is a random graph model based on the service contour. This is the set of technical resources involved in the provision of this service. In this formulation, the assessment of the reliability of the service is based on the reliability of elements which constitute the telecommunications network (graph), nodes (vertices) and communication lines (edges). At the same time, the availability factors of nodes and lines are determined by the design features of the distribution environment, as well as the technical means used to organize them. The purpose of this work is to develop an approach to analyzing the reliability of telecommunication networks which support protective switching mechanisms for one protected and one backup sections.Methods. The following methods are used: theory of random graphs, matrices, probabilities and computer modeling.Results. The elements of the route, both basic and reserving, are divided into three groups. The first indicates permanent unchangeable parts of the paths, the second group identifies the reserved sections, and the third group indicates the reserving sections. At the same time, each of the reserved and reserving sections is formed on the basis of specified preferences. They are usually aimed at increasing the resulting reliability, although other rules may be used. In the case of protective switching schemes for one protected section and one backup sections, a variant of forming routes used for further calculations of the reliability indicator is shown.Conclusions. Using the example of a backbone network, the study shows that the use of protective switching mechanisms for the case of one required transmission route demonstrates a significant increase in reliability, with the exception of the use of protective switching in sections. This is primarily due to the topology features of the network under consideration.

Causal learning by infants and young children: From computational theories to language practices.

Causal reasoning-the ability to reason about causal relations between events-is fundamental to understanding how the world works. This paper reviews two prominent theories on early causal learning and offers possibilities for theory bridging. Both theories grow out of computational modeling and have significant areas of overlap while differing in several respects. Explanation-Based Learning (EBL) focuses on young infants' learning about causal concepts of physical objects and events, whereas Bayesian models have been used to describe causal reasoning beyond infancy across various concept domains. Connecting the two models offers a more integrated approach to clarifying the developmental processes in causal reasoning from early infancy through later childhood. We further suggest that everyday language practices offer a promising space for theory bridging. We provide a review of selective work on caregiver-child conversations, in particular, on the use of scaffolding language including causal talk and pedagogical questions. Linking the research on language practices to the two cognitive theories, we point out directions for further research to integrate EBL and Bayesian models and clarify how causal learning unfolds in real life. This article is categorized under: Psychology > Learning Cognitive Biology > Cognitive Development.

Count-free Weisfeiler–Leman and group isomorphism

We investigate the power of counting in Group Isomorphism. We first leverage the count-free variant of the Weisfeiler–Leman Version I algorithm for groups [J. Brachter and P. Schweitzer, On the Weisfeiler–Leman dimension of finite groups, in 35th Annual ACM/IEEE Symp. Logic in Computer Science, eds. H. Hermanns, L. Zhang, N. Kobayashi and D. Miller, Saarbrucken, Germany, July 8–11, 2020 (ACM, 2020), pp. 287–300, doi:10.1145/3373718.3394786] in tandem with bounded non-determinism and limited counting to improve the parallel complexity of isomorphism testing for several families of groups. These families include: Direct products of non-Abelian simple groups. Coprime extensions, where the normal Hall subgroup is Abelian and the complement is an [Formula: see text]-generated solvable group with solvability class poly log log [Formula: see text]. This notably includes instances where the complement is an [Formula: see text]-generated nilpotent group. This problem was previously known to be in [Formula: see text] [Y. Qiao, J. M. N. Sarma and B. Tang, On isomorphism testing of groups with normal Hall subgroups, in Proc. 28th Symp. Theoretical Aspects of Computer Science, Dagstuhl Castle, Leibniz Center for Informatics, 2011), pp. 567–578, doi:10.4230/LIPIcs. STACS.2011.567], and the complexity was recently improved to [Formula: see text] [J. A. Grochow and M. Levet, On the parallel complexity of group isomorphism via Weisfeiler–Leman, in 24th Int. Symp. Fundamentals of Computation Theory, eds. H. Fernau and K. Jansen, Lecture Notes in Computer Science, Vol. 14292, September 18–21, 2023, Trier, Germany (Springer, 2023), pp. 234–247]. Graphical groups of class [Formula: see text] and exponent [Formula: see text] [A. H. Mekler, Stability of nilpotent groups of class 2 and prime exponent, J. Symb. Logic 46(4) (1981) 781–788] arising from the CFI and twisted CFI graphs [J. -Y. Cai, M. Fürer and N. Immerman, An optimal lower bound on the number of variables for graph identification, Combinatorica 12(4) (1992) 389–410], respectively. In particular, our work improves upon previous results of Brachter and Schweitzer [On the Weisfeiler–Leman dimension of finite groups, in 35th Annual ACM/IEEE Symp. Logic in Computer Science, eds. H. Hermanns, L. Zhang, N. Kobayashi and D. Miller, Saarbrucken, Germany, July 8–11, 2020 (ACM, 2020), pp. 287–300, doi:10.1145/3373718.3394786]. Notably, each of these families was previously known to be identified by the counting variant of the more powerful Weisfeiler–Leman Version II algorithm. We finally show that the [Formula: see text]-ary count-free pebble game is unable to even distinguish Abelian groups. This extends the result of Grochow and Levet (ibid), who established the result in the case of [Formula: see text]. The general theme is that some counting appears necessary to place Group Isomorphism into [Formula: see text].

Labeled sample compression schemes for complexes of oriented matroids

We show that the topes of a complex of oriented matroids (abbreviated COM) of VC-dimension d admit a proper labeled sample compression scheme of size d. This considerably extends results of Moran and Warmuth on ample classes, of Ben-David and Litman on affine arrangements of hyperplanes, and of the authors on complexes of uniform oriented matroids, and is a step towards the sample compression conjecture – one of the oldest open problems in computational learning theory. On the one hand, our approach exploits the rich combinatorial cell structure of COMs via oriented matroid theory. On the other hand, viewing tope graphs of COMs as partial cubes creates a fruitful link to metric graph theory.

Changing the logic without changing the subject: the case of computability

Abstract In this paper, I argue against the thesis that the meaning of ‘computability’ is logic-dependent. I do this from a category-theoretic perspective. Applying a method due to Mortensen and Lavers [26], I show that we can dualize the internal logic of the effective topos, in order to obtain a model of paraconsistent computability theory. Since the dualization leaves the structural properties of universal constructions in the topos unchanged, in particular the properties of the natural numbers object, I conclude that, at least in this case, changing the logic does not change our characterization of computability.

Prioritising national healthcare service issues from free text feedback – A computational text analysis & predictive modelling approach

Patient experience surveys have become a key source of evidence for supporting decision-making and continuous quality improvement within healthcare services. To harness free-text feedback collected as part of these surveys for additional insights, text analytics methods are increasingly employed when the data collected is not amenable to traditional qualitative analysis due to volume. However, while text analytics techniques offer good predictive capabilities, they have limited explanatory features often required in formal decision-making contexts, such as programme monitoring or evaluation. To overcome these limitations, this study integrates computational text and predictive modelling as part of a Computational Grounded Theory method to determine the effect of quality gaps in care dimensions and their prioritisation from free-text feedback. The feedback was collected as part of a national survey to support decisions on continuous improvement in Maternity Services in Ireland. Our approach enables (1) operationalising the service quality lexicon in the context of maternity care to explain the effect of quality gaps in care dimensions on overall satisfaction from free-text comments; and (2) extending the service quality lexicon with two organisational and political decision-making concepts: “Salience” and “Valence”, for prioritising perceived quality gaps. These methodological affordances enable the extension of service quality theory to explicitly support the prioritisation of improvement decisions which before now required additional decision frameworks. Results show that tangibles-, process-, and reliability-related care issues have the highest importance in our study context. We also find that hospital contexts partly determine the relative importance of gaps in care dimensions.

A computational and experimental study of cis-trans isomeric pesticides based on collision-induced dissociation of high-resolution mass spectrometry.

Pesticide isomers are widely available in agricultural production and may vary widely in biological activity, potency, and toxicity. Chromatographic and mass spectrometric analysis of pesticide isomers is challenging due to structural similarities. Based on liquid chromatography time-of-flight mass spectrometry, identification of cis-trans isomeric pesticides was achieved through retention time, characteristic fragment ions, and relative abundance ratio. Furthermore, theoretical and basic research has been conducted on the differences in characteristic fragment ions and their relative abundance ratios of cis-trans isomers. On the one hand, the cleavage pathways of six cis-trans isomers were elucidated through collision-induced dissociation to explain different fragment ions of the isomers. On the other hand, for those with the same fragment ions but different abundance ratios, energy-resolved mass spectrometry combined with computational chemical density functional theory in terms of kinetics, thermodynamics, and bond lengths was employed to explain the reasons for the differences in characteristic fragment ions and their abundance ratios. A high-resolution mass spectrometry method was developed for the separation and analysis of cis-trans isomers of pesticides in traditional Chinese medicine Radix Codonopsis, and six pesticide isomers were distinguished by retention time, product ions, and relative abundance ratios. The limits of quantification of the six pesticides were up to 10μg/kg, and the linear ranges of them were 10-200 μg/kg, with coefficients of determination (R2) > 0.99, which demonstrated the good linearity of the six pesticides. The recoveries of the pesticides at spiked concentrations of 10, 20, and 100 μg/kg reached 70-120% with relative standard deviations ≤20%. It was demonstrated that the application of the method was well suited for accurate qualitative and quantitative analysis for isomers with different structures, which could avoid false-negative results caused by ignoring other isomers effectively.

RESEARCH OF ALGORITHMS FOR SEARCHING PRIMITIVE ELEMENTS OF A FINITE FIELD OF HIGH ORDER

One of the most important unsolved and notoriously difficult problems in computational finite field theory is the development of a fast algorithm for constructing primitive roots in a finite field. It is known that for many applications, instead of a primitive root, just an element of high multiplicative order is sufficient. Such applications include, but are not limited to, cryptography, coding theory, pseudorandom number generation, and combinatorial schemes. Explicit constructions of high-order elements usually rely on combinatory methods that can provide a provable lower bound on the order, but this does not compute the exact order. Its execution usually implies knowledge of the factorization of the order. Ideally, we should be able to get a primitive element for any finite field in a reasonable amount of time. However, if the simple factorization of the group order is unknown, it is difficult to achieve the goal. Thus, we set the task of constructing an element, probably of a high order. This article discusses various algorithms that find a high-order element for general or special finite fields. This work also represents another contribution to the theory of Gauss periods over finite fields and their generalizations and analogues, which have already proven their usefulness for a number of different applications.

Snapshot spectral imaging: from spatial-spectral mapping to metasurface-based imaging

Abstract Snapshot spectral imaging technology enables the capture of complete spectral information of objects in an extremely short period of time, offering wide-ranging applications in fields requiring dynamic observations such as environmental monitoring, medical diagnostics, and industrial inspection. In the past decades, snapshot spectral imaging has made remarkable breakthroughs with the emergence of new computational theories and optical components. From the early days of using various spatial-spectral data mapping methods, they have evolved to later attempts to encode various dimensions of light, such as amplitude, phase, and wavelength, and then computationally reconstruct them. This review focuses on a systematic presentation of the system architecture and mathematical modeling of these snapshot spectral imaging techniques. In addition, the introduction of metasurfaces expands the modulation of spatial-spectral data and brings advantages such as system size reduction, which has become a research hotspot in recent years and is regarded as the key to the next-generation snapshot spectral imaging techniques. This paper provides a systematic overview of the applications of metasurfaces in snapshot spectral imaging and provides an outlook on future directions and research priorities.

Similarity in evoked responses does not imply similarity in macroscopic network states

Abstract It is commonplace in neuroscience to assume that if two tasks activate the same brain areas in the same way, then they are recruiting the same underlying networks. Yet computational theory has shown that the same pattern of activity can emerge from many different underlying network representations. Here we evaluated whether similarity in activation necessarily implies similarity in network architecture by comparing region-wise activation patterns and functional correlation profiles from a large sample of healthy subjects (N = 242). Participants performed two executive control tasks known to recruit nearly identical brain areas, the color-word Stroop task and the Multi-Source Interference Task (MSIT). Using a measure of instantaneous functional correlations, based on edge time series, we estimated the task-related networks that differed between incongruent and congruent conditions. We found that the two tasks were much more different in their network profiles than in their evoked activity patterns at different analytical levels, as well as for a wide range of methodological pipelines. Our results reject the notion that having the same activation patterns means two tasks engage the same underlying representations, suggesting that task representations should be independently evaluated at both node and edge (connectivity) levels.

Computability and non-monotone induction

Non-monotone inductive definitions were studied in the late 1960’s and early 1970’s with the aim of understanding connections between the complexity of the formulas defining the induction steps and the ordinals measuring the rank of the inductive process. In general, any type 2 functional will generate an inductive process, and in this paper we will view non-monotone induction as a functional of type 3. We investigate the associated computation theory of this functional inherited from the Kleene schemes and we investigate the associated companion of sets with codes computable in the functional of non-monotone induction. The interest in this functional is motivated from observing that constructions via non-monotone induction appear to be natural in classical analysis. There are two groups of results: We establish strong closure properties of the least ordinal without a code computable in the functional of non-monotone induction, and we provide a characterisation of the class of functionals of type 3 computable from this functional, a characterisation in terms of sequential operators working in transfinite time. We will also see that the full computational power of non-monotone induction is required when this principle is used to construct functionals witnessing the compactness of the Cantor space and of closed, bounded intervals.

Qualitative and quantitative analysis of pesticide isomers based on collision-induced dissociation of high-resolution mass spectrometry

Pesticide isomers are widely present in agricultural production, while their biological activity, efficacy, and toxicity may vary significantly. Due to structural similarity, chromatographic and mass spectrometric analysis of isomeric pesticides are challenging. In this experiment, representative isomeric pesticides with great differences in toxicity and maximum residue limits among countries were studied. Based on collision-induced dissociation (CID) of high-resolution mass spectrometry, the fragmentation pathways of substituent position isomer, functional group position isomer, carbon frame isomer, functional group isomer, and cis–trans isomer were analyzed to attribute fragment ions. In addition, for the isomers with the same product ions and different abundance ratios, the abundance differences at different energy-resolved mass spectrometry were analyzed, which was combined with the computational chemical density functional theory to simulate the specific process of fragmentation and to explain the reasons for the differences in fragment ions and abundance ratios. Based on the above study, a high-resolution mass spectrometry method was established for the separation and analysis of pesticide isomers. Twelve pesticide isomers were distinguished by retention time, fragment ions, and relative abundance ratio. This method was applied to the detection of real fruit and vegetable samples.

An in-principle super-polynomial quantum advantage for approximating combinatorial optimization problems via computational learning theory.

It is unclear to what extent quantum algorithms can outperform classical algorithms for problems of combinatorial optimization. In this work, by resorting to computational learning theory and cryptographic notions, we give a fully constructive proof that quantum computers feature a super-polynomial advantage over classical computers in approximating combinatorial optimization problems. Specifically, by building on seminal work by Kearns and Valiant, we provide special instances that are hard for classical computers to approximate up to polynomial factors. Simultaneously, we give a quantum algorithm that can efficiently approximate the optimal solution within a polynomial factor. The quantum advantage in this work is ultimately borrowed from Shor's quantum algorithm for factoring. We introduce an explicit and comprehensive end-to-end construction for the advantage bearing instances. For these instances, quantum computers have, in principle, the power to approximate combinatorial optimization solutions beyond the reach of classical efficient algorithms.

Statistical inference for a two-parameter Rayleigh distribution under generalized progressive hybrid censoring scheme

The two-parameter Rayleigh distribution, as an extended distribution of the Rayleigh distribution, has been widely applied in reliability analysis. With the introduction of the location parameter, two-parameter Rayleigh distribution becomes more flexible in fitting real-data. In this paper, based on generalized progressively hybrid censored(GPHC) sample from the two-parameter Rayleigh distribution, Classical and Bayesian inferences are discussed. The Newton-Raphson(NR) and Expectation-Maximization(EM) algorithms are used to compute the maximum likelihood estimates(MLEs). As well as the asymptotic confidence interval(ACI) estimation is obtained through the asymptotic distribution theory of maximum likelihood estimation(MLE) and computation of the observed Fisher information matrix. In Bayesian frame, the estimation of unknown parameters and prediction of future observable are taken into consideration. Due to Bayesian estimation is challenging to compute precisely and for the purpose of comparison, the Lindley's approximation, the Tierney-Kadane(TK) approximation and Markov chain Monte Carlo(MCMC) method are employed to obtain Bayesian estimates. Then, combining the MCMC algorithm mentioned in the article, the one- and two- samples Bayesian prediction are obtained. Finally, the simulation results are provided and a real-life data set is used for illustration purpose.

Modeling Effects of Rumination on Free Recall Using ACT-R.

Ruminative thinking, characterized by a recurrent focus on negative and self-related thought, is a key cognitive vulnerability marker of depression and, therefore, a key individual difference variable. This study aimed to develop a computational cognitive model of rumination focusing on the organization and retrieval of information in memory, and how these mechanisms differ in individuals prone to rumination and individuals less prone to rumination. Adaptive Control of Thought-Rational (ACT-R) was used to develop a rumination model by adding memory chunks with negative valence to the declarative memory. In addition, their strength of association was increased to simulate recurrent negative focus, thereby making it harder to disengage from. The ACT-R models were validated by comparing them against two empirical datasets containing data from control and depressed participants. Our general and ruminative models were able to recreate the benchmarks of free recall while matching the behavior exhibited by the control and the depressed participants, respectively. Our study shows that it is possible to build a computational theory of rumination that can accurately simulate the differences in free recall dynamics between control and depressed individuals. Such a model could enable a more fine-tuned investigation of underlying cognitive mechanisms of depression and potentially help to improve interventions by allowing them to more specifically target key mechanisms that instigate and maintain depression.

An Analysis of Tennenbaum's Theorem in Constructive Type Theory

Tennenbaum's theorem states that the only countable model of Peano arithmetic (PA) with computable arithmetical operations is the standard model of natural numbers. In this paper, we use constructive type theory as a framework to revisit, analyze and generalize this result. The chosen framework allows for a synthetic approach to computability theory, exploiting that, externally, all functions definable in constructive type theory can be shown computable. We then build on this viewpoint, and furthermore internalize it by assuming a version of Church's thesis, which expresses that any function on natural numbers is representable by a formula in PA. This assumption provides for a conveniently abstract setup to carry out rigorous computability arguments, even in the theorem's mechanization. Concretely, we constructivize several classical proofs and present one inherently constructive rendering of Tennenbaum's theorem, all following arguments from the literature. Concerning the classical proofs in particular, the constructive setting allows us to highlight differences in their assumptions and conclusions which are not visible classically. All versions are accompanied by a unified mechanization in the Coq proof assistant.

Exploring the Conceptual Framework of Mobile Learning Technology

The idea of introducing new technologies to education is not new, and as a result, research on this topic has been carried out for years. However, the rate of introduction of new technologies in higher education in Uzbekistan is very slow. The purpose of this article is to propose a conceptual framework for the development of mobile learning, in particular, the introduction of mobile applications into the educational process in primary education. This goal is achieved by analyzing the existing measures and the existing foundations of mobile education, which are used to improve the quality of education through the active use of information and communication technologies. The proposed system includes three main elements: applied computing, information systems, and theory of computation. It is important that each of them is done correctly and that there is continuity between them.

Computational high‐pressure chemistry: Ab initio simulations of atoms, molecules, and extended materials in the gigapascal regime

AbstractThe field of liquid‐phase and solid‐state high‐pressure chemistry has exploded since the advent of the diamond anvil cell, an experimental technique that allows the application of pressures up to several hundred gigapascals. To complement high‐pressure experiments, a large number of computational tools have been developed. These techniques enable the simulation of chemical systems, their sizes ranging from single atoms to infinitely large crystals, under high pressure, and the calculation of the resulting structural, electronic, and spectroscopic changes. At the most fundamental level, computational methods using carefully tailored wall potentials allow the analytical calculation of energies and electronic properties of compressed atoms. Molecules and molecular clusters can be compressed either via mechanochemical approaches or via more sophisticated computational protocols using implicit or explicit solvation approaches, typically in combination with density functional theory, thus allowing the simulation of pressure‐induced chemical reactions. Crystals and other periodic systems can be routinely simulated under pressure as well, both statically and dynamically, to predict the changes of crystallographic data under pressure and high‐pressure crystal structure transitions. In this review, the theoretical foundations of the available computational tools for simulating high‐pressure chemistry are introduced and example applications demonstrating the strengths and weaknesses of each approach are discussed.This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Simulation Methods

Research on the hydrodynamic performance of propellers under oblique flow conditions

The phenomenon of oblique water inflow is widespread in the operation of thrusters, which will cause adverse effects on the hydrodynamic performance of thrusters. In order to investigate the hydrodynamic performance and stress variation of the propeller in oblique flow, based on computational fluid dynamics theory, this paper takes the DTMB4119 propeller as the research object and conducts numerical simulation research on the propeller in oblique flow by solving the RANS equation. By calculating the open water performance curve and surface pressure distribution of the propeller, the rationality of the numerical method and the meshing are verified. Considering the flow field information such as velocity, oblique flow angles, flow line distribution, and pressure distribution, the changes in hydrodynamic characteristics of the propeller are simulated and analyzed. The results show that the uneven distribution of pressure on the propeller blade surface increases with a decrease in the advance coefficient. The force pulsation amplitude of a single blade increases with an increase in oblique flow angles. With the increase in oblique flow angles, the thrust, torque, and efficiency of the propeller show different increasing trends. With the increase in propeller advance coefficient, propeller thrust and torque decrease gradually, and propeller efficiency increases gradually. By using mature propellers, this paper has more reference value for studying the flow field around the ship hull and the hydrodynamic performance of propellers in the process of ship maneuvering.